Weight/RPM

I got my MSX 140 running pretty good. The TPS was bad so I changed it, and took her out for a ride today. I went to the calmest part of the lake, and ran her wide open. The fastest I could hit was 62mph, and 6700rpm. I know the MPH is not totally accurate because its not a GPS reading but the RPM was 6600 and for a few seconds it was 6700. My ski has 25hrs on it, is 6700 good enough? Will I get more RPM if there is a lighter rider on it? I weigh 275. Just wondered if I need to do some tweaking to it, or if its good enough in relation to me riding it.